repair sony es xm 5026 just lost a channel

was running a pair of tweeters and the left channel started making a scatchy sound then went out.
it still has a quiet scatchy sound . i just disconnected the amp and will use a ppi for now. i really love the sq of the sony very clean and precise..i`d love to get the sony repaired if possible.
any ideals as to what went wrong and or any repair options for this sweet oldschool amp?